1. Field of the Invention
The present invention relates to a medial treatment instrument configured so as to grip a biotissue as well as coagulate and cut the biotissue.
2. Description of the Related Art
Various medical treatment instruments for coagulating and cutting a biotissue have been conventionally known. For example, an apparatus for sealing and cutting a biotissue disclosed in the specification of U.S. Pat. No. 6,267,761 (hereinafter, referred to as prior art document) includes a pair of conductors arranged in parallel to each other, and each conductor includes at its end portion an electrode protruding in a direction perpendicular to the axial direction thereof. When the apparatus is used, the conductors are shifted in their axial directions to bring their electrodes close to each other, thereby gripping the biotissue between the electrodes. In this state, a coagulation high-frequency voltage is applied between the electrodes to generate thermal energy, and the biotissue is coagulated between the electrodes by use of thus-generated thermal energy.
However, the apparatus of the aforementioned prior art document for sealing and cutting a biotissue merely has a function of pinching the biotissue. When it is desired to cut the biotissue after coagulation, instead of applying a coagulation high-frequency voltage, it is required to apply between the electrodes a cutting high-frequency voltage (for example, a high-frequency voltage having a current waveform different from that of the coagulation high-frequency voltage) capable of generating thermal energy higher than the coagulation high-frequency voltage (see lines 49 to 50 in the second paragraph of the prior art document), and shift the electrodes toward each other at the same time. As described above, in order to coagulate and cut a biotissue by use of the sealing and cutting apparatus of the prior art document, the special electric power generator is required that generates a voltage for coagulation and a voltage for cutting respectively. This results in not only increased cost of the high-frequency power source but also large-sized high-frequency power source.
FIG. 7 in the prior art document discloses a structure in which the opposed surfaces of the electrodes are formed with recesses and projections engageable with each other. However, the apparatus of the prior art document cuts a biotissue only by use of the force applied in the direction of bringing the electrodes close to each other, that is, only by use of the force applied in the direction of gripping the biotissue. In this arrangement, even if the electrodes are formed with recesses and projections, the electrodes merely deform the biotissue into a thin form therebetween, and cannot cut the biotissue without utilizing the aforementioned cutting high-frequency voltage.
Further, if the recesses and projections are sharp-shaped to cut a biotissue, the surface of the biotissue is likely to be damaged when merely pinched by the electrodes. The biotissue damaged before coagulation is liable to bleed. This is not acceptable.
The present invention has been made in view of the problems described above, and an objective of the present invention is to provide a medical treatment instrument which can coagulate and cut a biotissue even only by use of a high-frequency power source only capable of generating a coagulation high-frequency voltage.